1. Field of the Invention
The present invention relates to a smoke detector equipped with an insect screen for preventing entry of insects into a smoke detecting space, as well as to an insect screen.
2. Description of the Related Art
FIGS. 19 to 22 show a commonly employed photoelectric smoke detector. FIG. 19 is a longitudinal cross-sectional view of the smoke detector; FIG. 20 is a transverse cross-sectional view of the smoke detector; FIG. 21 is a layout and construction drawing of a smoke detecting section; and FIG. 22 is a disassembly view of the smoke detector.
As shown in FIGS. 19 and 20, a terminal board 203 is housed in an exterior cover 201, and a shield case 204 is fixedly attached to the interior of the terminal board 203. A smoke detecting section main body 205 is fitted to the terminal board 203, and a printed board 208 is provided on the smoke detecting section main body 205. A plurality of smoke inlets 202 are formed along the circumference of the exterior cover 201.
A smoke detecting section cover 211 is removably attached to the lower surface of the smoke detecting section main body 205. Smoke inlets 215 are formed in the circumferential wall of the smoke detecting section cover 211. A plurality of labyrinthine members 213 are formed inside the circumferential wall. An insect screen 214 is integrally provided on the smoke detecting section 211.
A light-emission element 221, such as an infrared LED or the like, is housed in a light-emission holder 217 provided on the lower surface of the smoke detecting section main body 205. A light-receiving holder 216 houses a light-receiving element 220, such as a photodiode PD or the like. As can be seen from FIG. 21, the optical axis of the light-emission element 221 and the optical axis of the light-receiving element 220 are arranged so as to cross each other in the center of a smoke detecting space and at an angle of, for example, 70xc2x0. Here, reference numeral 228 designates an infrared LED for test purpose, and 232 designates a plate member having a slit formed therein.
As shown in FIG. 22, the above-described smoke detector is built by means of assembling together the terminal board 203 having fitting hardware 209 fixed thereon; the shield case 204; packing 207, the printed board 208; the smoke detecting section main body 205; the smoke detecting section cover 211; and the exterior cover 201.
In many cases, the insect screen 214 used in a commonly employed smoke detector is made of metal. As shown in FIG. 22, the insect screen 214 is provided so as to cover the smoke detecting section cover 211 constituting the labyrinthine elements of the smoke detecting section. In order to attain an improvement in ease of production and the strength of a smoke detector, an insect screen is integrally formed with a smoke detecting section during a molding operation (see Japanese Patent Publication No. Hei 5-78879).
Such an insect screen used with the smoke detector is formed by means of rolling a flat metal plate into a ring shape, hexagonal holes being formed in the metal plate, and attaching the thus-rolled metal plate to a position around labyrinthine elements of a smoke detecting section or integrally embedding the metal plate into the smoke detecting section during a molding operation. Thus, production of the smoke detector becomes complicated.
In the case of a smoke detector in which an insect screen is integrally formed with labyrinthine elements of a smoke detecting section, the insect screen cannot be replaced after production, even when replacement is desired. In such a case, a smoke detecting cover constituting labyrinthine elements or a smoke detecting section main body must be replaced inconveniently. Another problem of the smoke screen is that insects which favor narrow areas sometime intrude holes of the insect screen.
The present invention has been conceived in light of such drawbacks of the commonly used smoke detector, and it is an object of the present invention to provide a smoke detector which is easy to build and is provided with a low-cost insect screen, as well as an insect screen for use with the smoke detector.
The present invention provides a smoke detector which includes a smoke detecting section defining a smoke detecting space and detects occurrence of fire by detection of smoke flowing into the smoke detection space, the sensor comprising:
an insect screen which is formed from a soft material of mesh structure and is arranged around the smoke detecting section.
The smoke detecting section is open toward the periphery and the bottom, and the insect screen is arranged so as to fully cover the periphery of the smoke detecting section and the open bottom of the smoke detecting section. The insect screen is made from permeable fabric woven from soft metal fiber or chemical fiber. Alternatively, fiber impregnated with a repellent is used as the insect screen. The insect screen is fixedly sandwiched between an interior circumferential edge of an exterior cover and an exterior circumferential edge of a smoke detecting main body.
Thus, permeable cloth woven from fiber is used as the insect screen. In contrast with a commonly employed insect screen made by means of etching a metal plate, the fabric insect screen has a higher airflow permeability. In a case where a repellent is applied to an insect screen, since the insect screen is made of fabric, the fiber is sufficiently impregnated with a repellent, thus exhibiting an insect-proofing effect over a long period of time. Even when meshes are slightly wide, the insect-proofing effect prevents intrusion of insects. and does not have any special fixing structure. Hence, the insect screen can be readily removed by means of removal of only the exterior cover. Thus, easy removal and replacement of an insect screen is implemented.
The present invention also provides an insect screen for preventing intrusion of insects into a smoke detecting space of a smoke detector. The insect screen is characterized by being made of permeable fabric woven from metal or chemical fiber. As mentioned above, so long as permeable cloth woven from fiber is used as an insect screen, a higher airflow permeability can be attained as compared with a case where a commonly employed insect screen is made from a metal plate through etching. So long as a repellent is applied to fiber, the fiber is sufficiently impregnated with a repellent. Thus, an insect-proofing effect can be exhibited over a long period of time. Further, even in a case where meshes are slightly wide, the insect-proofing effect an be exhibited over a long period of time. Further, even in a case where meshes are slightly wide, the insect-proofing effect prevents intrusion of insects into the insect screen.